Temporal range: Middle Cambrian–Recent (total group)
|Genera and species|
|Wikispecies has information related to: Loricifera|
Loricifera (from Latin, lorica, corselet (armour) + ferre, to bear) is a phylum of very small to microscopic marine cycloneuralian sediment-dwelling animals with 36 described species, in eight genera. Aside from these described species, there are approximately 100 more that have been collected and not yet described. Their sizes range from 100 µm to ca. 1 mm. They are characterised by a protective outer case called a lorica and their habitat, which is in the spaces between marine gravel to which they attach themselves. The phylum was discovered in 1983 by Roberto Ramos, in Roscoff, France. They are among the most recently discovered groups of Metazoans. They attach themselves quite firmly to the substrate, and hence remained undiscovered for so long. The first specimen was collected in the 1970s, and later described in 1983. They are found at all depths, in different sediment types, and in all latitudes.
The animals have a head, mouth and digestive system as well as a lorica. The armor-like lorica consists of a protective external shell or case of encircling plicae. There is no circulatory system and no endocrine system. Many of the larvae are acoelomate, with some adults being pseudocoelomate, and some remaining acoelomate. Development is generally direct, though there are so-called Higgins larvae, which differ from adults in several respects. The animals have two sexes as adults. Very complex and plastic life cycles of pliciloricids include also paedogenetic stages with different forms of parthenogenetic reproduction. They are not known to be present in the fossil record.
Morphological studies have traditionlally placed the phylum in the vinctiplicata with the Priapulida; this plus the Kinorhyncha constitutes the taxon Scalidophora. The three phyla share four characters in common — chitinous cuticle, rings of scalids on the introvert, flosculi, and two rings of introvert retracts. However, mounting molecular evidence indicates a closer relationship with the nematomorpha.
The loriciferans are believed to be miniaturized descendants of a larger organism perhaps resembling the Cambrian fossil Sirilorica. However, the fossil record of the microscopic non-mineralized group is (perhaps unsurprisingly) scarce, so it is difficult to trace out the phylum's evolutionary history in any detail.
In anoxic environment
Three species of Loricifera have been found in the sediments at the bottom of the L'Atalante basin in Mediterranean Sea, more than 3,000 meters down, the first multicellular organisms known to spend their entire lives in an oxygen-free environment. They are able to do this because they rely on hydrogenosomes (or similar organelles) instead of on mitochondria for energy.
The newly reported animals complete their life cycle in the total absence of light and oxygen, and they are less than a millimetre in size. They were collected from a deep basin at the bottom of the Mediterranean Sea, where they inhabit a nearly salt-saturated brine that, because of its density (> 1.2 g/cm3), does not mix with the waters above. As a consequence, this environment is completely anoxic and, due to the activity of sulfate reducers, contains sulphide at a concentration of 2.9 mM. Despite such harsh conditions, this anoxic and sulphidic environment is teeming with microbial life, both chemosynthetic prokaryotes that are primary producers, and a broad diversity of eukaryotic heterotrophs at the next trophic level.
- Armorloricus davidi Kristensen & Gad, 2004
- Armorloricus elegans Kristensen & Gad, 2004
- Armorloricus kristenseni Heiner, 2004
- Phoeniciloricus simplidigitatus Gad, 2004
- Pliciloricus cavernicola
- Pliciloricus corvus Gad, 2005
- Pliciloricus dubius Higgins & Kristensen, 1986
- Pliciloricus enigmaticus Higgins & Kristensen, 1986
- Pliciloricus gracilis Higgins & Kristensen, 1986
- Pliciloricus hadalis Kristensen & Shirayama 1988
- Pliciloricus leocaudatus Heiner & Kristensen, 2005
- Pliciloricus orphanus Higgins & Kristensen, 1986
- Pliciloricus pedicularis Gad 2005
- Pliciloricus profundus Higgins & Kristensen, 1986
- Pliciloricus senicirrus Gad, 2005
- Pliciloricus shukeri Heiner & Kristensen, 2005
- Rugiloricus carolinensis Higgins & Kristensen, 1986
- Rugiloricus cauliculus Higgins & Kristensen, 1986
- Rugiloricus ornatus Higgins & Kristensen, 1986
- Rugiloricus polaris Gad and Arbizu, 2005
- Titaniloricus inexpectatovus Gad, 2005
- Peel, John S.; Stein, Martin; Kristensen, Reinhardt Møbjerg (9 August 2013). "Life Cycle and Morphology of a Cambrian Stem-Lineage Loriciferan". PLoS ONE. 8 (8): e73583. Bibcode:2013PLoSO...873583P. doi:10.1371/journal.pone.0073583. PMC . PMID 23991198.
- Kristensen, R. M. (2009). "Loricifera, a new phylum with Aschelminthes characters from the meiobenthos". Journal of Zoological Systematics and Evolutionary Research. 21 (3): 163–80. doi:10.1111/j.1439-0469.1983.tb00285.x.
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- Gad, Gunnar (17 June 2005). "Successive reduction of the last instar larva of Loricifera, as evidenced by two new species of Pliciloricus from the Great Meteor Seamount (Atlantic Ocean)". Zoologischer Anzeiger. 243 (4): 239–71. doi:10.1016/j.jcz.2004.09.001.
- Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D., eds. (2004). Invertebrate Zoology (7th ed.). p. 776. ISBN 978-0-03-025982-1.
- Heiner, Iben. "Preliminary account of the Loriciferan fauna of the Faroe Bank (NE Atlantic)". Annales Societatis Scientiatum Færoensis Supplementum. 41: 213–9.
- Heiner, Iben; Kristensen, Reinhardt Møbjerg (18 March 2005). "Two new species of the genus Pliciloricus (Loricifera, Pliciloricidae) from the Faroe Bank, North Atlantic". Zoologischer Anzeiger. 243 (3): 121–38. doi:10.1016/j.jcz.2004.05.002.
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- Peel, John S. (March 2010). "A Corset-Like Fossil from the Cambrian Sirius Passet Lagerstätte of North Greenland and Its Implications for Cycloneuralian Evolution". Journal of Paleontology. 84 (2): 332–40. doi:10.1666/09-102R.1. JSTOR 40605520.
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- Milius, Susan (April 9, 2010). "Briny deep basin may be home to animals thriving without oxygen". Science News.
- Mentel, Marek; Martin, William (6 April 2010). "Anaerobic animals from an ancient, anoxic ecological niche". BMC Biology. 8: 32. doi:10.1186/1741-7007-8-32. PMC . PMID 20370917.
- Bernhard, Joan M.; Morrison, Colin R.; Pape, Ellen; Beaudoin, David J.; Todaro, M. Antonio; Pachiadaki, Maria G.; Kormas, Konstantinos Ar.; Edgcomb, Virginia P. (2015). "Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins". BMC Biology. 13: 105. doi:10.1186/s12915-015-0213-6. PMC . PMID 26652623.
- Danovaro, Roberto; Dell'Anno, Antonio; Pusceddu, Antonio; Gambi, Cristina; Heiner, Iben; Kristensen, Reinhardt Mobjerg (2010). "The first metazoa living in permanently anoxic conditions". BMC Biology. 8: 30. doi:10.1186/1741-7007-8-30. PMC . PMID 20370908.
- Fox-Skelly, Jasmin (25 January 2017). "BBC Earth: There is one animal that seems to survive without oxygen". BBC News.
- Heiner, Iben (2008). "Rugiloricus bacatus sp. nov. (Loricifera ‐Pliciloricidae) and a ghost‐larva with paedogenetic reproduction". Systematics and Biodiversity. 6 (2): 225–47. doi:10.1017/S147720000800265X.
- Ramel, Gordon. "The Brush Heads (Phylum Loricifera)".[self-published source?]
- "Can animals thrive without oxygen?". Woods Hole Oceanographic Institution. January 28, 2016.